Not necesarily - the liver can still be effective when part of it has been removed, if that is necessary, and I think (if my GCSE biology memory is treating me well today) it is the only organ in the body that is able to regenerate itself, so even if some is removed, it is able to grow back.

Cancer is a disease that often comes with a whole lot of wrong misconceptions, and many people often think it is the end. Some people are lucky, and any cancer is removed in an operation, but others may need follow up treatment such as radio- and/or chemotherapy, and possibly even further operations to remove other tumours, or do reconstruction. Also, many people live with, and have the condition managed with medication by their medical teams for many years.

One really important thing is to make sure your Mum's friend remains positive, and is aware of all of the outcomes of her illness, both good and bad.